Let's imagine that every food source except one suddenly becomes extremely toxic for humans and no matter what we try to do with them, they stay toxic.

I'd like to know if there's some food source humanity could survive on only by eating it, obviously no one is gonna be specially healthy by just eating from a single food source, but as long as it would allow humanity to survive for a long time, even if barely, it would be valid.

I think that potatoes are good as a single source that would allow for a typical person to survive even some months, but in a story that takes a lot of years (30-40 years) I don't think it would be enough, although if it were the case I'd like to know.

Is there any food source that would fulfill the mentioned condition? If so, which one?

Edit: As I see one answer that didn't fulfill my intention I'm explaining better. The food source must stay with whatever their natural nutrients were, any try of getting outside of that nutrients would end in toxicity.

There's also some magic involved in the story, so even if it's not realistic it can be considered this way.

  • $\begingroup$ Useful article in Popular Science on this topic: popsci.com/nutrition-single-food-survival $\endgroup$ – SRM Mar 31 '18 at 1:31
  • $\begingroup$ There is almost nothing we eat that is in its "natural" state, we have been altering our food for thousands of years. Another big issue is such a wide ranging single crop becomes vulnerable to disease. $\endgroup$ – John Mar 31 '18 at 2:32
  • $\begingroup$ Would beef plus cheese made from cow milk count as a single source or two, how about turkey and their eggs? $\endgroup$ – John Mar 31 '18 at 4:41

There is no modern species of plant or animal will provide all the nutrients necessary. Soy has decent amount of protein, carbs, and fat, but it does not nearly have all the vitamins we need.

But there is a "cheat". Let one crop remain viable. If people can eat it, then so can the animals. Pigs and goats are good choices. if humans can survive the cataclysm, then so will animals.

The crop could be something where you can eat different parts of the plant, so you get your carbs and fat from the typical part of the crop, and vitamins from the leaves. And then protein from animals that eat the same crop.

If you really do not want animals in addition to crop, use people instead of animals. Invent social mechanism for who gets eaten: underclasses, lottery, over certain age, second child, etc.

Otherwise, use magic or genetic engineering of the crop to compensate for missing vitamins.


No, not given your criteria anyway, but it is possible with two foods

even ar most nutrient rich foods like sweet potatoes, Brassicae, eggs or fish, are still deficient is some vitamins or minerals. Many like shellfish also have fairly hard limits on production. Now it might be possible to genetically alter them to produce those nutrients as well, breeds of rice and wheat have both been successfully altered to be more nutritious, there is just little incentive to design an all in one food.

Eating an animal (as long as you eat everything) can fulfill your nutritional requirements but has its own problems. Now there are human populations that survive off eating a single livestock animal and nothing else but the majority of the world's population would not survive off such a diet, things like gout would be widespread.

If you limited yourself to say two or three sources (say one animal and one plant) this becomes plausible, A high nutrient yield plant like brassica, sweet potato or wheat, plus meat or fish is quite sustainable. The animal produce provides the broad spectrum and the plant source provides an alternative calorie source to the meat and provides starch, fiber, and extra vitamins. Works even better if the animal is a two for one and supplies milk or eggs.

This does bring up the question of would beef plus cheese made from cow milk count as a single source or two, how about turkey and their eggs?


Even if there were such a crop that could allow humans to survive, I only have to think of the Irish Potato Famine to see how bad an idea this is. At least in reality - in fiction it might add a lot to your story, but I wouldn't plot it this way.

Depending on a single food source also means that anything that hurts the food source causes famine. The Irish Potato Famine, or the Great Famine occurred between 1845 and 1849. About 1,000,000 people died and a similar number emigrated.

If there is magic, then perhaps this magic could be used to cleanse the toxicity from other crops for the vitamins and minerals that the main non-toxic crop can't provide as well as providing a back-up food source.

Mankind has survived on toxic food in many places. Sometimes it is prepared with specialized cooking, such as boiling it multiple times to remove the poisons. Sometimes such as the Fugu fish in Japan chefs are trained to cut out the poison glands, however people still die from eating these fish, and much as I like seafood, I think I'll skill this particular fish.


The situation is unrealistic, but yes, we could survive on a single food source if we had the technology to add the necessary vitamins and trace elements to it. Or supplement it with vitamin pills and other things to ensure we get everything we need.

Peanuts would be my choice, but some people are allergic, so potatoes or another root crop would be fine.

  • $\begingroup$ Individual people might die of peanut allergies, but humanity could survive... if peanuts can be made to be a complete food. I’m thinking that’s not possible the more I investigate this question on Web. $\endgroup$ – SRM Mar 31 '18 at 1:25
  • $\begingroup$ @SRM peanuts don't need to be a complete food if we can supplement it with vitamin pills and other dietary supplements widely available right now $\endgroup$ – Kilisi Mar 31 '18 at 1:50
  • $\begingroup$ look at the research that went into Soylent, which is an effort to answer this exact challenge. They were unable to find any single food that could do it, even supplemented. Soylent is a blend of multiple inputs for that reason. $\endgroup$ – SRM Mar 31 '18 at 5:04
  • $\begingroup$ @SRM which is why I said 'IF' in my answer $\endgroup$ – Kilisi Mar 31 '18 at 21:34
  • $\begingroup$ Sure, but if we could do that, we could do it to any food, so it is kind of a non-answer. If we can do that kind of augmentation, peanuts are no better answer than kale. Or anything, for that matter, really. It would be taking multiple food sources and combining them. That’s not single source. $\endgroup$ – SRM Apr 1 '18 at 2:21

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